Forcing all paths (within plugins) to be https

Hello. I installed an SSL certificate for one of my client's websites. I have a donation page with a donation form, using, and I needed the page to be https.

I put some PHP code to force that page to be https (which worked fine).
I went into settings > general, and changed the Wordpress Address (URL) to be https, as well.

Once I make these two changes, most of the paths reflected https, however, I am getting a warning from the SSL certificate that says there are still paths using the regular http.

Upon further investigation, it seems that some of my plugins are using http hardcoded links within the plugin, and I really don't want to manually change all of this, because when the plugins get updated the changes I make will be overwritten.

Is there a way to force all paths within the site to reflect https without having to change everything manually?

As a reference, please take a look at the donate page in question: